5.1 Halfbridge Configuration
A common configuration used for the MCP14LH2106(4) is a half-bridge (see Figure 5-1). In a half-bridge configuration the source of the high-side MOSFET (QH) and the drain of the low-side MOSFET (QL) are connected, ensuring the line (VS) is both the return for the high side in the gate driver IC and the output of the half-bridge. When QH is ON and QL is OFF, VS swings to high voltage, and when QH is OFF and QL is ON, VS swings to GND. Hence, the output switches from GND to high voltage at the frequency of HIN and LIN, this line drives a transformer for a power supply, or a coil on a motor.
In this half-bridge configuration, high voltage DC is input to the MOSFETs, and converted to a high voltage switching signal to output to load (Figure 5-1). The MOSFETs operate in saturation mode and an important function of the gate driver is to turn ON the MOSFET quickly to minimize switching losses from the linear region of the MOSFET (turn ON and turn OFF). The MCP14LH2106(4) has a typical rise/fall time of 100 ns/35 ns for a 1 nF load.
Another important function of the gate driver IC in a half-bridge configuration is to convert the logic of the control signals (MCP14LH2106(4) operates at logic 3.3V), to a voltage and current level sufficient to drive the gate of the MOSFET and IGBT. This requires driving large currents initially to turn ON/turn OFF the MOSFET quickly. Also, the floating well of the high-side allows high voltage configurations during bootstrap operation.